The proposed research is a prospective longitudinal investigation into the speech-sound production abilities of young patients with a diagnosis of severe traumatic brain injury (TBI). The first two aims of the investigation are to determine the rate and level of consonant mastery over a 12-month period in children who have suffered severe TBI. To achieve these objectives, spontaneous speech samples will be elicited monthly from each child. Speech sampling will begin when the child demonstrates spontaneous speech-like vocalizations and will continue for 12 months after the first sampling session at which the child produces ten intelligible words. Speech growth curves for individual children with severe TBI as well as for the group as a whole will be calculated using the Percentage of Consonants Correct metric (PCC) (Shriberg et al. 1997a). Group and individual PCC growth curves will then be compared statistically to a normal PCC growth curve derived from existing data. The third aim is to compare the consonant production errors of children injured earlier (12-48 months of age) and later (49-95 months of age) in the speech development process, after referencing their performance to uninjured age peers. Children injured in the earlier stage of speech development are expected to have relatively more errors in which consonants are omitted altogether or replaced by different consonants, but we expect similar rates of consonant distortion errors in the earlier and later groups. Finally, we will test multivariate models of five variables predicted to influence the rate and level of consonant mastery in these children. The findings from this research will provide much-needed data on the rate and level of speech-sound change of children injured at various points in the speech development process as well as new information on the variables that predict speech-sound change.